Gas and air mixing apparatus



Oct. 9, 1951 P. E. PEAcocK, JR

GAS AND AIR MIXING APPARATUS 4 Sheets-Sheet 1 Filed June 23, 1949 n fl n m INVENTOR. P401 1-". P0900: dz.

BY W AM ATTORNEYS Oct. 9, 1951 P. E. PEACOCK, JR

GAS AND AIR MIXING APPARATUS Filed June 25, 1949 4 Sheets-Sheet 2 ATTORNEYS Oct. 9, 1951 P. E. PEACOCK, JR 2,570,373

GAS'AND AIR MIXING APPARATiJs Filed June 25, 1949 4 Shets-Sheet 4 T/MEz C'l/fiRGE Pan/real.

I N V E N TOR. P1404 E Pawn/c die.

BY WYM ATTORNEY Patented Oct. 9, 1951 UNITED STATES PATENT OFFICE GAS AND AIR MIXING. APPARATUS Paul E. Peacock, Jr., Westfield, N. J.

Application June 2-3, 1949, Serial. No. 1005946 4 Claims. 1

This invention relates to apparatus for producing and. supplying combustible gas-air mixtures', utilizing liquefied petroleum gas of the methane series, such as propane and mixtures of propane. and butane.

()ne of the aims of the invention is to provide apparatus. for making and supplying a diluted liquefied petroleum gas of substantially constant calorific value and pressure for use in municipal and industrial plants.

Another aim of the invention is to provide safe and dependable apparatus of the type set forth having a variable capacity over a wide range, which can be employed. without expensive storage facilities to supply diluted gas at constant pressure forsuch uses.

Another aim of the. invention is to provide a novel control system employing a series of gas and air mixers of different capacities to. insure the production of a mixture of substantially constant calorific value in response to widely differentload demands.

A further aim of the invention is to provide such a system having novel means to equalize the temperatures of the gas and air employed in making up the mixture to maintain a substan tial-ly constant calorific value of the mixture.

A further aim of the invention is to provide an alarm system and safety appurtenances to insure continuous and safe operation without requiring the attention of skilled technicians.

Other aims, objects and advantages of the invention will appear in the specification. when considered in connection with the accompanying drawings, wherein:

Fig. l is a diagrammatic lay-out of a com plete mixing plant for liquefied petroleum gas embodying the invention;

Fig. 2 is a diagrammatic plan view of the gas and air mixing apparatus shown in Fig. 1;

Fig. 3 is a side elevation, partly in section, of a single mixing unit and appurtenances connected thereto;

Fig. 4 is a sectional view of an air control valve for one. of the-mixers;

Fig. 5 is a diagrammatic illustration of electrical control apparatus employing storage. batteries for operating the system; and

Fig. 6 is a sectional view of one of the electrical control switches for the mixers.

With the understanding that the apparatus is capable of many industrial uses, it will be described as a municipal gas plant employing propane or a. propane-butane mixture as the fuel. Normal vaporfrom propane or a propane-butane thanis generally distributed by existing distribution. systems; hence, it. is diluted with air, so that its B. t. u. content is comparable to that of the original gas. In some instances, where it is anticipated that natural gas will. become available in the near future, the B. t. u. of the gas may be comparable to natural gas even though it is, replacing a lower B. t. u. manufactured. gas. In other words, the B. t. u. or the, gas from the mixing plant can be varied to meet the requirementsof the specific. application.

Referring, to the general lay-out of theplant shown inFig. 1, gas in the form of propane vapor is supplied by a storage. tank In through a supply conduit II, to a series of mixers located in the mixing room I2 of a building having separate rooms l3 and M for housing the control equipment andthe storage. batteries, respectively. The pressure of the propane vapor is utilized through a jet type of. compressor, commonly known as a venturi,. for inspirating air into the vapor stream and diluting the same to the desired B. t. 11. content. By regulation of the propane vapor pressure and control of the intake air supply, the B. t. u. may be regulated and the discharge pressure controlled. Certain other controls which will be. hereinafter described, operate with and control the operation of the mixer so as to. maintain a. substantially constant pressure in the distribution mains .during varying load demands. 7

Referring to. Fig. 2, the propane vapor is conducted through a pair of pressure regulator valves IS in branches connected to. the conduit ll', two such pressure reducing regulators being employed, so that either one may be removed and repaired or replaced while the other is employed. A valved conduit l1, by-passing both branches carrying th pressure reducing regulators, may be provided to permit amanually controlled supply of gas to be fed to the mixers if both regulators fail to function. The gas pressure is reducedto, say 10 to 20 pounds, and the gas is conducted to the mixers through an air-gas heat exchanger to equalize the temperature of the gas and air.

In this example, atmospheric air is. supplied to the. mixers through a large conduit l8 leading from the outside into themixing room [2 and the gascond-uit H has a finned section is passing through. the air conduit. The air conduit also has an. inlet branch 20 inside the mixing room and dampers 2| and 22 are provided in the two intakes, one opened and the other closed, to permit either outside air or room air to be supplied to the air conduit. This is especially desirable during very cold weather. The two dampers may be operated simultaneously by a single operating lever 23. During very cold weather the damper 22 is opened to admit heated air from the mixing room to the air conduit.

The air conduit [8 is in the form of a manifold and the gas conduit ll, passing therethrough, leads through a vertical branch to a gas manifold 24, both to supply air and gas to the mixers. A drip pipe 25 carrying heat exchanging fins and an electrical resistance heating coil is connected to the vertical run of the gas pipe I i, and the finned section 19 and the manifold 24 are inclined downwardly to the left in Fig. 2, to permit any condensate to drain into it and be re-vaporized. The lower end of the drip tube is provided with a drain valve 26 to permit heavy oil fractions and any water in the condensate to be discharged.

A plurality of branch pipes Zia-41c are shown as being connected to the air manifold i 8 and a corresponding plurality of branches 28a, 28b28e are connected to the gas manifold 24 to supply air and gas to the mixers, as clearly shown in Fig. 2.

Referring to Fig. 3, showing the first of a, series of mixers and its air and gas sup ly connections, it will be noted that the vertical branch pipe 21a is shown as being connected by a T 29 and horizontal branch 30 to an automatic control valve 3|, shown in detail in Fig. 4; while the other vertical branch of the T carries an extension of the pipe toward the floor of the control room, being open at its bottom, so that any leaking gas may be sucked into this nice and delivered with the air to the mixers. This branch pi e is connected to the lowermost portion of the air manifold and the first mixer is used more often than the rest of the mixers because it is designed to carry the minimum load capacity. The air branch 30 is also shown as carrying a throttle valve 32 having a graduated scale 33 so that its opening may be adjusted to control the volume of air therethrou h, and it is connected to the intake chamber of the first Venturi-mixer 34a, into which gas at a. constant pressure is introduced through the gas branch pipe 28a. L

In this example, the supply of air to the mixer is controlled by the suction in the suction chamber 35 of the mixer by means of a diaphragmoperated control valve member 36 in the valve casing 3|, as shown in Fig. 4 of the drawings. A diaphra m 31 is arranged in a housing removably connected to the casing of valve RI, and the lower half of the housing is connected by a small conduit 38 to the suction chamber 35. the arran ernent being such that suction created in the chamber 35 will be transmitted to the dia hragm casin and cause the valve 35 to open when gas is delivered throu h the mixer. Gas pressure in the mixer chamber 35 will act throu h the pipe 38 on the diaphragm to close the valve 36 when the mixer is not working. The air valve has a double seat 39, one for the val e 36 and another for a back flow check valve 40, shown as being carried by a perforated leather or flexible diaphragm 4i secured to the valve casing by a cap or bonnet 42. The arrangement is such that if the diaphragm-operated control valve 36 fails to function, the back flow check valve will close automatically by gravity and prevent the escape of gas from the mixing chamber 35 when the mixer is not functioning. The upper section of the diaphragm housing is shown as having a small opening 43 serving as a breather opening into the control valve chamber.

Gas under constant pressure is adapted to be supplied to the mixer through the gas branch 28a carrying an ordinary diaphragm controlled pressure reducing regulator valve 44 which is adapted to be set to supply the gas at any desired pressure. From the regulator valve 44, the gas passes through a valved conduit 45 which is shown as being connected by a branch 46 and tube 41 to the diaphragm casing 48 to operate the regulator valve. The pipe 45 carries an ordinary cut-off valve 49 controlled by a solenoid 50a, which is adapted to be energized by automatic supply control mechanism hereinafter to be described. The valved conduit 45 is connected to communicate with the rear end of the Venturi-mixer 34a, and the mixer has an inlet chamber 51 formed by a partition 52 carrying a removable jet nozzle 53. The rear end of the housing is closed by a screw cap 54 to afford access to the jet nozzle. A pressure gauge 55 is also shown as being connected to communicate with the gas chamber 5| in order that the pressure of the gas may be observed.

In the event that either the pressure reducing regulator or the solenoid controlled valve in the gas branch fails, it is desirable to be able to supply gas to the mixer under manually controlled pressure. For this purpose, a valved bypass conduit 56 is connected to the supply branch 28a and leads directly, through a T, to the intake gas chamber 5| of the mixer 34a, as shown. The pipe branches are shown as having a plurality of manually operable cut-off valves adapted to be manipulated in an obvious manner for this purpose, as will be seen in Fig. 3. While the flow of gas through the pressure reducing regulator valve and the solenoid valve is cut off, these appurtenances may be removed and repaired or replaced without interrupting the service. Also, the pipe connections are such that manually controlled gas can be by-passed around the regulator valve and directed through the solenoid valve 49a.

The supply of air at atmospheric pressure, and at a temperature equalized with that of the gas, is controlled by the suction created in the suction chamber 35 of the Venturi-mixer, which acts upon the air control valve 3|, as hereinbefore explained. The opening of the throttle valve 32 changes the volume flow of air to the mixer and only requires an initial adjustment for a given constant B. t. u. of the gas.

The Venturi-mixer 34a delivers the gas-air mixture through a nipple or conduit 51 to the gas main or header 58, and the conduit has a manual cut-off valve 59 adapted to be closed to permit the mixer to be removed for repairs or for replacement, as will be obvious from an inspection of Fig. 3.

The supply of gas to the mixer is adapted to be cut oif automatically by the solenoid operated valve 49a in response to pressure variations in the gas main. This is accomplished by a pressure-responsive switch controlled mechanism herein-after to be described, connected to be actuated by the pressure in a branch tube 60 communicating with the gas main or the header 58.

It will be understood that all of the mixers and their valve controlled connections are identical, except for the size and capacity of the mixers, and they are connected, side by side, to the gas main header, as shown in Fig. 2. However, the capacity of the mixers is progressively increased to take care of fluctuating load demands. The

capacity of the first mixer, which has been described, is such as to take care of the minimum load demand; While the capacity of the last mixer issufiicient to take care of the expected maximum demand on the system. The arrangement is such that the mixers are adapted to be used in succession and individually to take care of difierent normal load demands between the minimum load and the maximum expected load. The idea is to avoid the use of a mixer of very great capacity to take care of a relatively small load, because the proportion of gas and air will be somewhat disturbed upon starting and stopping the operation of the mixer, due to fluctuations in the air flow. Furthermore, the arrangement is such that, when an abnormal load is imposed upon the system, due to the rupture of a main, or other causes, the control mechanism will operate to employ all or any desired number of the mixers at the same time.

Since the mixing apparatus is designed to be operated without the use of ordinary gas storage tanks, it is necessary that the control system shall not be subject to interruption, due to temporary power failures of the usual source of current supply. To that end, the automatic solenoid valves are adapted to be operated by a series of storage batteries 6| adapted to be charged periodically by the source of alternating current,

represented by the power line 62, through an automatic timer charge control 63 and charger 64. The arrangement is such that the batteries may be fully charged at any desired intervals, in a manner well known in the art.

In this example, the negative side of the batteries is shown as being connected by a conductor 65 through a series of manually controlled switches 66a, Slit-65c, and a series of branch conductors 61 to one terminal of eachof the solenoids 50c, 5017-506; while the positive side of the batteries is connected to the other terminals of the solenoids by a main conductor 68 through the manual switches 66a to 666, and branch conductors 69 and double-acting, tilting mercury bulb switches 10a, lllb--I0e, which are adapted to be operated in response to predetermined pressure drops in the gas main communicated through the tube 80'.

As shown in Fig. 6, each of the mercury switches is actuated by an adjustable bellows diaphragm H connected to a spring-urged linkage 12 having an arm connected to a pivoted lever 13 carrying the mercury tube. The mercury tubes carry a pair of switch terminals at each end. The arrangement is such that when the pressure in. the main or header 58 is a predetermined amount below normal or the required working pressure, the mercury tubes will swing downward to the right or to their on positions and close the circuit through the contacts at the right hand end. The successive bellows are adjusted to operate the mercury switches responsive to successively increased pressure drops in the gas main. The bellows are normally expanded when the pressure is normal and their springs are progressively weakened to permit them to contact at progressively lower pressures in the gas main.

The positive conductor branch 69 is connected to one of the terminals at the right hand end of each mercury tube 10a; while the other terminal at that end of the tube is connected by a conductor 14 to one of the terminals at the left hand endof the next succeeding mercury tube 10b, the other terminal at that end of the second tube being. connected by a branch. conductor 15 to the positive terminal of the first solenoid 50a. The main positive conductor 68 is connected to the right hand terminals of the mercury tube switches 10b, 10c, 10d, and We, in the same manner, as has just been described in connection with the mercury tube 10a, and the arrangement is such that the circuit to each of the successive solenoids is closed, when one of the mercury tubes is tilted to the right, while the next succeeding mercury tube remains tilted to the left. Incidentally, the two terminals at the left hand end of the first mercury tube 10a are not connected in the circuit. When that switch tube is tilted to the right, current fiows to the first solenoid 50a through the right hand terminals of that switch and the left hand terminals of the next succeeding switch, which is tilted to the left. Thus, the first solenoid valve 49a is opened to admit liquefied petroleum gas vapor to the first and smallest mixer 34a.

The first mixer will remain in operation as long as its capacity is required to meet the minimum load demand: that is to say, as long as the pres sure drop in the main or header 58 is sufficient to operate the first mercury switch 10a. If the first mixer builds up the pressure to the required normal, say 6 ounces, in the gas main, the first mercury switch will open the circuit and shut oil the supply of liquefied petroleum. gas vapor to the mixer. Now, when the load demand exceeds the capacity of the first mixer, the pressure drop will increase enough to close the second mercury switch by swinging its tube downwardly to the right, simultaneously breaking the circuit to the first solenoid previously closed through the contacts in the left hand end of the second mercury tube. The circuit to the second solenoid 50b will be closed through the second and third mercury tube switches in the same manner as the circuit to the first solenoid was closed. Then, the second mixer, alone, will be placed in operation and will remain in operation as long as its greater capacity is sufiicient to supply the increased demand. However, when it builds up the pressure in the main to nearly normal, due to its greater capacity, the second mercury switch will be swung again to its Oil position and again close the circuit to the first solenoid, so that the first mixer will again be operated. If the load demand increases beyond the capacity of the second mixer, a still further resulting pressure drop will operate the third mercury switch and thus cause the third and still larger mixer 34c to take over the job of supplying the demand. In like manner, the fourth and the fifth mixers brought into operation as the load increases beyond the capacities of the respective preceding mixers. Incidentally, the circuit to the last solenoid 59c is completed directly through the contacts at the right hand end of the last mercury switch me.

To maintain the gas and air mixture substantiallyuniform. under varying load condition, when the various mixers are suddenly started and stopped, a surge tank T6 is shown in Fig. 2, as being connected to the gas main 58 by valved branches 1'! and '18, so that the mixture may be diverted therethrough.

Due to leakage and other causes, such systems are sometimes subjected to abnormal load demands beyond the capacity of the largest mixer used to supply the expected peak load. To avoid the added expense of providing an abnormally large mixer, separate control means is provided to cause all of the inactive mixers to operate simultaneously when the largest mixer 34c fails. to

supply the demand and the pressure drop increases sufliciently to operate a sixth mercury switch 10 tilting it to its On position while the largest mixer 34e remains in operation, to call on all of the mixers to assist in supplying the abnormal load. To that end, the battery leads or conductors B and 68 are shown as being connected through a sixth manually operable switch 66 and branch conductors l9 and 80, to energize and operate a plurality of normally open relay switches 8|a, 8lb, Bio and 8Id' to close circuits to the first four solenoids independently of the mercury switches a to 17d which normally operate them. The contacts at the right hand end of the mercury switch 10 are connected to the conductor branch 80 and the respective relays are connected to close the solenoid circuits by bridgin contacts in positive branch conductors 82 leading from the conductor 69 to the positive branches 15. When this happens, all of the mixers will be operated simultaneously until the pressure drop is reduced sufliciently to permit the mercury switch 10 to be returned to its normal Off position or tilted to the left, as shown. Obviously, this recycling operation may be applied to selected ones of the mixers.

To enable an operator to determine whether the system is functioning properly, audible and visual signals are provided to warn him that either the main power supply is interrupted, or that the propane vapor supply to the several mixers has reduced in pressure to a predetermined low point. In this example, a low voltage electric bell or other audible signal 83 is shown as being connected to the battery leads by conductors 84 and 85 through a normally closed relay switch 86 and a double-pole snap-action, no- Off position switch 81, both to close contacts in the conductor 85. The relay switch 86 is connected to the power circuit by conductors 88 and 89 and this switch is held open when the relay is energized. When the power supply to the timer charge control 63 is interrupted by power failure from any cause, the relay switch 86 becomes deenergized and this allows the switch to close contacts in the low voltage conductor 85 to the circuit to the audible signal 83. The double-pole, snap-action switch 81 is normally in a position that makes contact to signal 83 through low voltage conductor 85. The audible signal will sound until the power supply is restored to the timer charge control 63 or until the snap-action switch 8! is manually turned to the alternate position. When the snap-action switch 81 is manually turned to break the contact to the low voltage audible signal, such turning makes contact to signal light 94 through conductor 95 and causes this signal light to come on, the circuit being completed through conductors 95 and 96. If the signal light fails to light when snap-action switch 81 is turned manually, then it is evident that the power supply to timer charge control 63 has been interrupted and is the cause of the audible alarm. The signal light will indicate also that the alarm device has been turned off manually and, so long as the light is on, it will be a warning that the audible signal is inoperative.

The audible signal 83 is also adapted to be operated in response to an abnormal pressure drop in the propane vapor conduit 24. For this purpose, a tilting mercury switch 90 is connected by conductor branches 9| and 92 to the battery branch conductor 85 to by-pass the relay 86, so that the mercury switch can close the bell circuit independently of the relay switch. The mercury switch is similar to the switch 10a, but is designed to operate at the higher pressure maintained in the vapor conduit 24. This mercury switch is operated by any abnormal pressure drop in conduit 24 through branch conduit 93 which is connected to vapor conduit 24 (see branch in Fig. 2). When the mercury switch tilts to the right, due to a predetermined reduction in pressure in conduit 24, the bell circuit will be closed with the snap-action switch 81 in its bell circuit closing position.

In view of the fact that the several mixers are designed and connected to function as independent units, they may be removed, one at a time, for repairs and/or replacement without interrupting the operation of the system.

From the foregoing description, it will be seen that the improved mixing apparatus can be installed in lieu of a gas plant employing cumbersome and expensive storage facilities. Moreover, a system of this type can be installed at a relatively low cost as compared with other types and offers many advantages as a replacement for existing gas manufacturing plants; as a. stand-by or emergency supplement to such existing plants; and as an industrial plant or stand-by plant. It can be started up in a matter of minutes, as compared with other plants, which require hours of time and numerous skilled workmen. In all cases, the plant has the decided advantage of being substantially automatic in the mixing operations and does not require technically trained personnel in constant attendance. It can be used as a replacement or stand-by supply for either manufactured gas or natural gas. It will also be apparent that the apparatus embodies abundant safety appurtenances to insure dependable and continuous operation.

What is claimed is:

1. Apparatus for mixing liquefied petroleum gas vapor and air comprising, in combination, a plurality of Venturi-mixers of different capacities connected to a main to deliver mixed vapor and air thereto; a source of liquefied petroleum gas under pressure including conduits connected to the mixers and pressure reducing regulators to maintain the vapor at a substantially constant pressure; air conduits connected to the suction chambers of said Venturi-mixers, each including an automatic valve operative in response to the suction created in the respective Venturi-mixers by the delivered vapor; a valve in each of the vapor conduits adapted to be opened to admit vapor to the mixers; solenoids connected to open the respective vapor valves; pressure responsive means connected to the mixed gas main, includding a plurality of doublethrow mercury tube switches and bellows diaphragms connected thereto adjusted to effect operation thereof responsive to different pre-determined pressure drops in the mixed gas main; a source of low voltage current connected to said solenoids through said switches; and conductors connecting alternate ends of the successive switches, so that when any switch is tilted to its circuit closing position, it will break the circuit through the preceding switch and only one of the valves will be operated at a time as long as the capacity of the corresponding mixer is suflicient to supply the demand.

2. Apparatus, as set forth in claim 1, including a tilting mercury switch and a bellows diaphragm connected to the mixed gas main and adjusted to operate the switch responsive to an abnormal pressure drop in the main; a series of relay switches in the electric circuit controlled by said last named mercury switch and connected to the solenoids for all of the vapor valves except the one for the largest mixer, whereby when the largest mixer fails to supply the mixed gas demand and the last named mercury switch is operated by the abnormal pressure drop, all of the closed vapor valves will be opened simultaneously to operate all of the mixers.

3. Apparatus, as set forth in claim 1, wherein storage batteries are connected to supply the low voltage current for operating said solenoids, including automatic time controlled battery charging means utilizing utility electric current connected to charge the batteries periodically.

4. Apparatus, as set forth in claim 1, wherein storage batteries are connected to supply the low voltage current for operating said solenoids, including automatic time controlled battery charging means utilizing utility electric current connected to charge the batteries periodically; auto- 10 matic signal means connected in circuit with the source of charging current adapted to be energized due to an interruption in the supply of charging current; and an associated signal having a pressure operated control switch connected to the vapor supply line to be operated by an abnormal pressure drop therein.

PAUL E. PEACOCK, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,556 Heller Oct. 24, 1944 1,620,240 Smoot Mar. 8, 1927 1,834,130 McKee Dec. 1, 1931 2,148,509 Shafer Feb. 28, 1939 2,251,636 Robb Aug. 5, 1941 2,342,426 Ransome Feb. 22, 1944 

